"We had some guests taking risks and maybe getting a little too risky. If you had one incident where something did happen, it would be very tragic. We didn't want to wait for that to happen," park spokeswoman Jennifer Berthume said.

Since the park opened 38 years ago, lions have been able to walk right up next to the cars. Warning signs and zookeepers remind visitors to stay in their cars and keep their windows rolled up. But many visitors crack open a car window or a door, and some have gotten out and tried to feed the lions.

Officials at the Palm Beach County park said they had been considering a fence for years, fearing a serious injury or a lawsuit. In November they finally erected a barricade.

The park's other animals, which include antelope, buffalo and tortoises, can still roam next to cars. Those animals have always been kept separate from the lions.